This invention relates to a drum filter assembly which is suitable for use in aquaculture systems but which may be used in any other water treatment application.
Aquaculture has commonly been conducted by growing fish, prawns and other marine invertebrates in outdoor ponds. The ponds however eventually become polluted because faeces, uneaten food and algae work their way to the bottom of the ponds. This makes the ponds almost impossible to clean. In addition large quantities of valuable water are required to keep these systems functional. Other disadvantages are also associated with outdoor aquaculture systems. For example pests can eat stock, adverse weather conditions such as floods can cause stock loss by washing the stock away and very hot weather can cause growth of algal blooms which can kill the stock. In addition in very hot or very cold weather, the stock will stop growing. Muddy waters or disturbed water can also cause the stock to have an unpalatable taste.
In order to overcome the above disadvantages, indoor commercial aquaculture systems were introduced where fish or other marine invertebrates are grown in tanks placed in large buildings or sheds.
A disadvantage of the known systems is that the buildings or sheds housing the aquaculture system resemble a maze of pipes and plumbing as water is pumped between the system components such as tanks, filters, biological filters, foam fractionators, ultraviolet water treatment units and other water treatment components. These components are individual components which have to be set up in different parts of the building.
Drum filters have been a part of the aquaculture systems for filtering the water of fine waste particles created from waste food, faeces, and other extraneous matter. The majority of filters are electric motor driven off central drive shafts with bearings on which the drum filter is supported for rotation. In most cases the cleaning takes place through a centre mounted vertical disc through which the water must pass. The drum filters are separate units and include an outer housing which is specifically designed to hold the filter and its supporting components and to also hold the water. Water inlets and outlets must also be provided along with special float switches to activate a cleaning process when the water level rises.
As a general rule, during cleaning the water flow is stopped or bypassed which allows uncleaned water back into the fish tanks. If the water is stopped for any length of time, it can be very detrimental to the fish stock as in times of heavy stock loading, the fish can only stay alive for around six minutes before fatalities begin to occur. Another major drawback is that if a bearing or another major mechanical failure happens, removal the drum filter and all of the fittings is extremely time consuming and in many cases can lead to total stock losses. Cleaning of the current drum filters in any event is difficult as easy access cannot be had to the interior of the drum.